This invention relates to a moldable foot bed for insertion into a pair of shoes. More specifically, this invention relates to a laminated structure incorporating an inner sole and a foamed elastomer layer which is heat deformable to produce a conforming interface between a shoe last and the sole of the user's foot.
Shoes are manufactured to conform with a standard last while human feet display a much greater variety of form. Consequently, only a relatively small percentage of the populace can obtain a good and comfortable fit in standard shoes.
This problem has been long recognized and two standard approaches have evolved to alleviate it. One approach has been the provision of inner soles for fitting within a shoe to provide additional cushioning between the shoe last and the foot. The second approach has been to provide a molded insert patterned from the user's foot and inserted within the shoe.
Inner soles are typically constructed of an elastomeric foam material base often having a top, or foot contacting, cover of stretch nylon fabric or the like as is disclosed for example in U.S. Pat. No. 3,448,533. The stretch fabric is adhesively bonded to the base ply and provides a slick surface between the inner sole and the foot of the user. Another type of inner sole, also having a top cover of stretch fabric, is disclosed in the Wolpa patent, U.S. Pat. No. 4,167,834. The Wolpa inner sole consists of an open cell foam base which tends to compress and take a set under constant or sustained pressure. An elastic closed cell foam layer, thinner than the base, is provided intermediate the base and fabric covering.
The second approach, that of providing a molded insert patterned from the user's foot, is illustrated by U.S. Pat. No. 3,825,017. An inner sole is formed by first obtaining a negative impression of the foot of the user. The impression is then filled with plaster or the like to obtain a positive impression or casting. An inner sole composite material is then heat formed with pressure to provide a molded composite conforming to the user's foot. The composite is then trimmed for insertion into a shoe.
Another molded shoe insert is sold under the name "Conform'able" and is especially designed for use with ski boots. These inner sole inserts consist of a thermoplastic plate about one-eighth inch thick covered with a material routinely used for boot lining. They are semi-rigid after molding and are molded by causing the user to stand in a skier's stance on heated inner sole blanks while bracing against a frame to increase the pressure on the inner sole blanks.
While the prior art inner soles and molded inserts do alleviate a number of problems of discomfort, blistering and the like associated with the imperfect fit between an individual foot and a standard shoe, all fall short of providing maximum adaptability and foot protection. Specifically, a relatively slick surfaced inner sole such as those utilizing a stretch nylon top cover allows relative movement of the foot across the inner sole, a condition which can cause frictional blistering, rather than absorbing lateral movement within the inner sole structure. Shoe inserts molded to a user's foot in turn seldom conform to the last of the shoe itself and thus introduce new problems.